Re: [net-next RFC V5 4/5] virtio_net: multiqueue support

From: Jason Wang
Date: Mon Jul 23 2012 - 01:46:30 EST

On 07/20/2012 09:40 PM, Michael S. Tsirkin wrote:
On Thu, Jul 05, 2012 at 06:29:53PM +0800, Jason Wang wrote:
This patch converts virtio_net to a multi queue device. After negotiated
VIRTIO_NET_F_MULTIQUEUE feature, the virtio device has many tx/rx queue pairs,
and driver could read the number from config space.

The driver expects the number of rx/tx queue paris is equal to the number of
vcpus. To maximize the performance under this per-cpu rx/tx queue pairs, some
optimization were introduced:

- Txq selection is based on the processor id in order to avoid contending a lock
whose owner may exits to host.
- Since the txq/txq were per-cpu, affinity hint were set to the cpu that owns
the queue pairs.

Signed-off-by: Krishna Kumar<krkumar2@xxxxxxxxxx>
Signed-off-by: Jason Wang<jasowang@xxxxxxxxxx>
Overall fine. I think it is best to smash the following patch
into this one, so that default behavior does not
jump to mq then back. some comments below: mostly nits, and a minor bug.

Sure, thanks for the reviewing.

If you are worried the patch is too big, it can be split
differently
- rework to use send_queue/receive_queue structures, no
functional changes.
- add multiqueue

but this is not a must.

---
drivers/net/virtio_net.c | 645 ++++++++++++++++++++++++++++++-------------
include/linux/virtio_net.h | 2 +
2 files changed, 452 insertions(+), 195 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 1db445b..7410187 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -26,6 +26,7 @@
#include<linux/scatterlist.h>
#include<linux/if_vlan.h>
#include<linux/slab.h>
+#include<linux/interrupt.h>

static int napi_weight = 128;
module_param(napi_weight, int, 0444);
@@ -41,6 +42,8 @@ module_param(gso, bool, 0444);
#define VIRTNET_SEND_COMMAND_SG_MAX 2
#define VIRTNET_DRIVER_VERSION "1.0.0"

+#define MAX_QUEUES 256
+
struct virtnet_stats {
struct u64_stats_sync tx_syncp;
struct u64_stats_sync rx_syncp;
Would be a bit better not to have artificial limits like that.
Maybe allocate arrays at probe time, then we can
take whatever the device gives us?

Sure.
@@ -51,43 +54,69 @@ struct virtnet_stats {
u64 rx_packets;
};

-struct virtnet_info {
- struct virtio_device *vdev;
- struct virtqueue *rvq, *svq, *cvq;
- struct net_device *dev;
+/* Internal representation of a send virtqueue */
+struct send_queue {
+ /* Virtqueue associated with this send _queue */
+ struct virtqueue *vq;
+
+ /* TX: fragments + linear part + virtio header */
+ struct scatterlist sg[MAX_SKB_FRAGS + 2];
+};
+
+/* Internal representation of a receive virtqueue */
+struct receive_queue {
+ /* Virtqueue associated with this receive_queue */
+ struct virtqueue *vq;
+
+ /* Back pointer to the virtnet_info */
+ struct virtnet_info *vi;
+
struct napi_struct napi;
- unsigned int status;

/* Number of input buffers, and max we've ever had. */
unsigned int num, max;

+ /* Work struct for refilling if we run low on memory. */
+ struct delayed_work refill;
+
+ /* Chain pages by the private ptr. */
+ struct page *pages;
+
+ /* RX: fragments + linear part + virtio header */
+ struct scatterlist sg[MAX_SKB_FRAGS + 2];
+};
+
+struct virtnet_info {
+ u16 num_queue_pairs; /* # of RX/TX vq pairs */
+
+ struct send_queue *sq[MAX_QUEUES] ____cacheline_aligned_in_smp;
+ struct receive_queue *rq[MAX_QUEUES] ____cacheline_aligned_in_smp;
The assumption is a tx/rx pair is handled on the same cpu, yes?
If yes maybe make it a single array to improve cache locality
a bit?
struct queue_pair {
struct send_queue sq;
struct receive_queue rq;
};

Ok.
+ struct virtqueue *cvq;
+
+ struct virtio_device *vdev;
+ struct net_device *dev;
+ unsigned int status;
+
/* I like... big packets and I cannot lie! */
bool big_packets;

/* Host will merge rx buffers for big packets (shake it! shake it!) */
bool mergeable_rx_bufs;

+ /* Has control virtqueue */
+ bool has_cvq;
+
won't checking (cvq != NULL) be enough?

Enough, so has_cvq is dupliated with vi->cvq. I will remove it in next version.

/* enable config space updates */
bool config_enable;

/* Active statistics */
struct virtnet_stats __percpu *stats;

- /* Work struct for refilling if we run low on memory. */
- struct delayed_work refill;
-
/* Work struct for config space updates */
struct work_struct config_work;

/* Lock for config space updates */
struct mutex config_lock;
-
- /* Chain pages by the private ptr. */
- struct page *pages;
-
- /* fragments + linear part + virtio header */
- struct scatterlist rx_sg[MAX_SKB_FRAGS + 2];
- struct scatterlist tx_sg[MAX_SKB_FRAGS + 2];
};

struct skb_vnet_hdr {
@@ -108,6 +137,22 @@ struct padded_vnet_hdr {
char padding[6];
};

+static inline int txq_get_qnum(struct virtnet_info *vi, struct virtqueue *vq)
+{
+ int ret = virtqueue_get_queue_index(vq);
+
+ /* skip ctrl vq */
+ if (vi->has_cvq)
+ return (ret - 1) / 2;
+ else
+ return ret / 2;
+}
+
+static inline int rxq_get_qnum(struct virtnet_info *vi, struct virtqueue *vq)
+{
+ return virtqueue_get_queue_index(vq) / 2;
+}
+
static inline struct skb_vnet_hdr *skb_vnet_hdr(struct sk_buff *skb)
{
return (struct skb_vnet_hdr *)skb->cb;
@@ -117,22 +162,22 @@ static inline struct skb_vnet_hdr *skb_vnet_hdr(struct sk_buff *skb)
* private is used to chain pages for big packets, put the whole
* most recent used list in the beginning for reuse
*/
-static void give_pages(struct virtnet_info *vi, struct page *page)
+static void give_pages(struct receive_queue *rq, struct page *page)
{
struct page *end;

/* Find end of list, sew whole thing into vi->pages. */
for (end = page; end->private; end = (struct page *)end->private);
- end->private = (unsigned long)vi->pages;
- vi->pages = page;
+ end->private = (unsigned long)rq->pages;
+ rq->pages = page;
}

-static struct page *get_a_page(struct virtnet_info *vi, gfp_t gfp_mask)
+static struct page *get_a_page(struct receive_queue *rq, gfp_t gfp_mask)
{
- struct page *p = vi->pages;
+ struct page *p = rq->pages;

if (p) {
- vi->pages = (struct page *)p->private;
+ rq->pages = (struct page *)p->private;
/* clear private here, it is used to chain pages */
p->private = 0;
} else
@@ -140,15 +185,15 @@ static struct page *get_a_page(struct virtnet_info *vi, gfp_t gfp_mask)
return p;
}

-static void skb_xmit_done(struct virtqueue *svq)
+static void skb_xmit_done(struct virtqueue *vq)
{
- struct virtnet_info *vi = svq->vdev->priv;
+ struct virtnet_info *vi = vq->vdev->priv;

/* Suppress further interrupts. */
- virtqueue_disable_cb(svq);
+ virtqueue_disable_cb(vq);

/* We were probably waiting for more output buffers. */
- netif_wake_queue(vi->dev);
+ netif_wake_subqueue(vi->dev, txq_get_qnum(vi, vq));
}

static void set_skb_frag(struct sk_buff *skb, struct page *page,
@@ -167,9 +212,10 @@ static void set_skb_frag(struct sk_buff *skb, struct page *page,
}

/* Called from bottom half context */
-static struct sk_buff *page_to_skb(struct virtnet_info *vi,
+static struct sk_buff *page_to_skb(struct receive_queue *rq,
struct page *page, unsigned int len)
{
+ struct virtnet_info *vi = rq->vi;
struct sk_buff *skb;
struct skb_vnet_hdr *hdr;
unsigned int copy, hdr_len, offset;
@@ -225,12 +271,12 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
}

if (page)
- give_pages(vi, page);
+ give_pages(rq, page);

return skb;
}

-static int receive_mergeable(struct virtnet_info *vi, struct sk_buff *skb)
+static int receive_mergeable(struct receive_queue *rq, struct sk_buff *skb)
{
struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb);
struct page *page;
@@ -244,7 +290,7 @@ static int receive_mergeable(struct virtnet_info *vi, struct sk_buff *skb)
skb->dev->stats.rx_length_errors++;
return -EINVAL;
}
- page = virtqueue_get_buf(vi->rvq,&len);
+ page = virtqueue_get_buf(rq->vq,&len);
if (!page) {
pr_debug("%s: rx error: %d buffers missing\n",
skb->dev->name, hdr->mhdr.num_buffers);
@@ -257,13 +303,14 @@ static int receive_mergeable(struct virtnet_info *vi, struct sk_buff *skb)

set_skb_frag(skb, page, 0,&len);

- --vi->num;
+ --rq->num;
}
return 0;
}

-static void receive_buf(struct net_device *dev, void *buf, unsigned int len)
+static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
{
+ struct net_device *dev = rq->vi->dev;
struct virtnet_info *vi = netdev_priv(dev);
struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
struct sk_buff *skb;
@@ -274,7 +321,7 @@ static void receive_buf(struct net_device *dev, void *buf, unsigned int len)
pr_debug("%s: short packet %i\n", dev->name, len);
dev->stats.rx_length_errors++;
if (vi->mergeable_rx_bufs || vi->big_packets)
- give_pages(vi, buf);
+ give_pages(rq, buf);
else
dev_kfree_skb(buf);
return;
@@ -286,14 +333,14 @@ static void receive_buf(struct net_device *dev, void *buf, unsigned int len)
skb_trim(skb, len);
} else {
page = buf;
- skb = page_to_skb(vi, page, len);
+ skb = page_to_skb(rq, page, len);
if (unlikely(!skb)) {
dev->stats.rx_dropped++;
- give_pages(vi, page);
+ give_pages(rq, page);
return;
}
if (vi->mergeable_rx_bufs)
- if (receive_mergeable(vi, skb)) {
+ if (receive_mergeable(rq, skb)) {
dev_kfree_skb(skb);
return;
}
@@ -363,90 +410,91 @@ frame_err:
dev_kfree_skb(skb);
}

-static int add_recvbuf_small(struct virtnet_info *vi, gfp_t gfp)
+static int add_recvbuf_small(struct receive_queue *rq, gfp_t gfp)
{
struct sk_buff *skb;
struct skb_vnet_hdr *hdr;
int err;

- skb = __netdev_alloc_skb_ip_align(vi->dev, MAX_PACKET_LEN, gfp);
+ skb = __netdev_alloc_skb_ip_align(rq->vi->dev, MAX_PACKET_LEN, gfp);
if (unlikely(!skb))
return -ENOMEM;

skb_put(skb, MAX_PACKET_LEN);

hdr = skb_vnet_hdr(skb);
- sg_set_buf(vi->rx_sg,&hdr->hdr, sizeof hdr->hdr);
+ sg_set_buf(rq->sg,&hdr->hdr, sizeof hdr->hdr);
+
+ skb_to_sgvec(skb, rq->sg + 1, 0, skb->len);

- skb_to_sgvec(skb, vi->rx_sg + 1, 0, skb->len);
+ err = virtqueue_add_buf(rq->vq, rq->sg, 0, 2, skb, gfp);

- err = virtqueue_add_buf(vi->rvq, vi->rx_sg, 0, 2, skb, gfp);
if (err< 0)
dev_kfree_skb(skb);

return err;
}

-static int add_recvbuf_big(struct virtnet_info *vi, gfp_t gfp)
+static int add_recvbuf_big(struct receive_queue *rq, gfp_t gfp)
{
struct page *first, *list = NULL;
char *p;
int i, err, offset;

- /* page in vi->rx_sg[MAX_SKB_FRAGS + 1] is list tail */
+ /* page in rq->sg[MAX_SKB_FRAGS + 1] is list tail */
for (i = MAX_SKB_FRAGS + 1; i> 1; --i) {
- first = get_a_page(vi, gfp);
+ first = get_a_page(rq, gfp);
if (!first) {
if (list)
- give_pages(vi, list);
+ give_pages(rq, list);
return -ENOMEM;
}
- sg_set_buf(&vi->rx_sg[i], page_address(first), PAGE_SIZE);
+ sg_set_buf(&rq->sg[i], page_address(first), PAGE_SIZE);

/* chain new page in list head to match sg */
first->private = (unsigned long)list;
list = first;
}

- first = get_a_page(vi, gfp);
+ first = get_a_page(rq, gfp);
if (!first) {
- give_pages(vi, list);
+ give_pages(rq, list);
return -ENOMEM;
}
p = page_address(first);

- /* vi->rx_sg[0], vi->rx_sg[1] share the same page */
- /* a separated vi->rx_sg[0] for virtio_net_hdr only due to QEMU bug */
- sg_set_buf(&vi->rx_sg[0], p, sizeof(struct virtio_net_hdr));
+ /* rq->sg[0], rq->sg[1] share the same page */
+ /* a separated rq->sg[0] for virtio_net_hdr only due to QEMU bug */
+ sg_set_buf(&rq->sg[0], p, sizeof(struct virtio_net_hdr));

- /* vi->rx_sg[1] for data packet, from offset */
+ /* rq->sg[1] for data packet, from offset */
offset = sizeof(struct padded_vnet_hdr);
- sg_set_buf(&vi->rx_sg[1], p + offset, PAGE_SIZE - offset);
+ sg_set_buf(&rq->sg[1], p + offset, PAGE_SIZE - offset);

/* chain first in list head */
first->private = (unsigned long)list;
- err = virtqueue_add_buf(vi->rvq, vi->rx_sg, 0, MAX_SKB_FRAGS + 2,
+ err = virtqueue_add_buf(rq->vq, rq->sg, 0, MAX_SKB_FRAGS + 2,
first, gfp);
if (err< 0)
- give_pages(vi, first);
+ give_pages(rq, first);

return err;
}

-static int add_recvbuf_mergeable(struct virtnet_info *vi, gfp_t gfp)
+static int add_recvbuf_mergeable(struct receive_queue *rq, gfp_t gfp)
{
struct page *page;
int err;

- page = get_a_page(vi, gfp);
+ page = get_a_page(rq, gfp);
if (!page)
return -ENOMEM;

- sg_init_one(vi->rx_sg, page_address(page), PAGE_SIZE);
+ sg_init_one(rq->sg, page_address(page), PAGE_SIZE);

- err = virtqueue_add_buf(vi->rvq, vi->rx_sg, 0, 1, page, gfp);
+ err = virtqueue_add_buf(rq->vq, rq->sg, 0, 1, page, gfp);
if (err< 0)
- give_pages(vi, page);
+ give_pages(rq, page);

return err;
}
@@ -458,97 +506,104 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi, gfp_t gfp)
* before we're receiving packets, or from refill_work which is
* careful to disable receiving (using napi_disable).
*/
-static bool try_fill_recv(struct virtnet_info *vi, gfp_t gfp)
+static bool try_fill_recv(struct receive_queue *rq, gfp_t gfp)
{
+ struct virtnet_info *vi = rq->vi;
int err;
bool oom;

do {
if (vi->mergeable_rx_bufs)
- err = add_recvbuf_mergeable(vi, gfp);
+ err = add_recvbuf_mergeable(rq, gfp);
else if (vi->big_packets)
- err = add_recvbuf_big(vi, gfp);
+ err = add_recvbuf_big(rq, gfp);
else
- err = add_recvbuf_small(vi, gfp);
+ err = add_recvbuf_small(rq, gfp);

oom = err == -ENOMEM;
if (err< 0)
break;
- ++vi->num;
+ ++rq->num;
} while (err> 0);
- if (unlikely(vi->num> vi->max))
- vi->max = vi->num;
- virtqueue_kick(vi->rvq);
+ if (unlikely(rq->num> rq->max))
+ rq->max = rq->num;
+ virtqueue_kick(rq->vq);
return !oom;
}

-static void skb_recv_done(struct virtqueue *rvq)
+static void skb_recv_done(struct virtqueue *vq)
{
- struct virtnet_info *vi = rvq->vdev->priv;
+ struct virtnet_info *vi = vq->vdev->priv;
+ struct napi_struct *napi =&vi->rq[rxq_get_qnum(vi, vq)]->napi;
+
/* Schedule NAPI, Suppress further interrupts if successful. */
- if (napi_schedule_prep(&vi->napi)) {
- virtqueue_disable_cb(rvq);
- __napi_schedule(&vi->napi);
+ if (napi_schedule_prep(napi)) {
+ virtqueue_disable_cb(vq);
+ __napi_schedule(napi);
}
}

-static void virtnet_napi_enable(struct virtnet_info *vi)
+static void virtnet_napi_enable(struct receive_queue *rq)
{
- napi_enable(&vi->napi);
+ napi_enable(&rq->napi);

/* If all buffers were filled by other side before we napi_enabled, we
* won't get another interrupt, so process any outstanding packets
* now. virtnet_poll wants re-enable the queue, so we disable here.
* We synchronize against interrupts via NAPI_STATE_SCHED */
- if (napi_schedule_prep(&vi->napi)) {
- virtqueue_disable_cb(vi->rvq);
+ if (napi_schedule_prep(&rq->napi)) {
+ virtqueue_disable_cb(rq->vq);
local_bh_disable();
- __napi_schedule(&vi->napi);
+ __napi_schedule(&rq->napi);
local_bh_enable();
}
}

static void refill_work(struct work_struct *work)
{
- struct virtnet_info *vi;
+ struct napi_struct *napi;
+ struct receive_queue *rq;
bool still_empty;

- vi = container_of(work, struct virtnet_info, refill.work);
- napi_disable(&vi->napi);
- still_empty = !try_fill_recv(vi, GFP_KERNEL);
- virtnet_napi_enable(vi);
+ rq = container_of(work, struct receive_queue, refill.work);
+ napi =&rq->napi;
+
+ napi_disable(napi);
+ still_empty = !try_fill_recv(rq, GFP_KERNEL);
+ virtnet_napi_enable(rq);

/* In theory, this can happen: if we don't get any buffers in
* we will *never* try to fill again. */
if (still_empty)
- queue_delayed_work(system_nrt_wq,&vi->refill, HZ/2);
+ queue_delayed_work(system_nrt_wq,&rq->refill, HZ/2);
}

static int virtnet_poll(struct napi_struct *napi, int budget)
{
- struct virtnet_info *vi = container_of(napi, struct virtnet_info, napi);
+ struct receive_queue *rq = container_of(napi, struct receive_queue,
+ napi);
void *buf;
unsigned int len, received = 0;

again:
while (received< budget&&
- (buf = virtqueue_get_buf(vi->rvq,&len)) != NULL) {
- receive_buf(vi->dev, buf, len);
- --vi->num;
+ (buf = virtqueue_get_buf(rq->vq,&len)) != NULL) {
+ receive_buf(rq, buf, len);
+ --rq->num;
received++;
}

- if (vi->num< vi->max / 2) {
- if (!try_fill_recv(vi, GFP_ATOMIC))
- queue_delayed_work(system_nrt_wq,&vi->refill, 0);
+ if (rq->num< rq->max / 2) {
+ if (!try_fill_recv(rq, GFP_ATOMIC))
+ queue_delayed_work(system_nrt_wq,&rq->refill, 0);
}

/* Out of packets? */
if (received< budget) {
napi_complete(napi);
- if (unlikely(!virtqueue_enable_cb(vi->rvq))&&
+ if (unlikely(!virtqueue_enable_cb(rq->vq))&&
napi_schedule_prep(napi)) {
- virtqueue_disable_cb(vi->rvq);
+ virtqueue_disable_cb(rq->vq);
__napi_schedule(napi);
goto again;
}
@@ -557,13 +612,14 @@ again:
return received;
}

-static unsigned int free_old_xmit_skbs(struct virtnet_info *vi)
+static unsigned int free_old_xmit_skbs(struct virtnet_info *vi,
+ struct virtqueue *vq)
{
struct sk_buff *skb;
unsigned int len, tot_sgs = 0;
struct virtnet_stats *stats = this_cpu_ptr(vi->stats);

- while ((skb = virtqueue_get_buf(vi->svq,&len)) != NULL) {
+ while ((skb = virtqueue_get_buf(vq,&len)) != NULL) {
pr_debug("Sent skb %p\n", skb);

u64_stats_update_begin(&stats->tx_syncp);
@@ -577,7 +633,8 @@ static unsigned int free_old_xmit_skbs(struct virtnet_info *vi)
return tot_sgs;
}

-static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
+static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb,
+ struct virtqueue *vq, struct scatterlist *sg)
{
struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb);
const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;
@@ -615,44 +672,47 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)

/* Encode metadata header at front. */
if (vi->mergeable_rx_bufs)
- sg_set_buf(vi->tx_sg,&hdr->mhdr, sizeof hdr->mhdr);
+ sg_set_buf(sg,&hdr->mhdr, sizeof hdr->mhdr);
else
- sg_set_buf(vi->tx_sg,&hdr->hdr, sizeof hdr->hdr);
+ sg_set_buf(sg,&hdr->hdr, sizeof hdr->hdr);

- hdr->num_sg = skb_to_sgvec(skb, vi->tx_sg + 1, 0, skb->len) + 1;
- return virtqueue_add_buf(vi->svq, vi->tx_sg, hdr->num_sg,
+ hdr->num_sg = skb_to_sgvec(skb, sg + 1, 0, skb->len) + 1;
+ return virtqueue_add_buf(vq, sg, hdr->num_sg,
0, skb, GFP_ATOMIC);
}

static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
{
struct virtnet_info *vi = netdev_priv(dev);
+ int qnum = skb_get_queue_mapping(skb);
+ struct virtqueue *vq = vi->sq[qnum]->vq;
int capacity;

/* Free up any pending old buffers before queueing new ones. */
- free_old_xmit_skbs(vi);
+ free_old_xmit_skbs(vi, vq);

/* Try to transmit */
- capacity = xmit_skb(vi, skb);
+ capacity = xmit_skb(vi, skb, vq, vi->sq[qnum]->sg);

/* This can happen with OOM and indirect buffers. */
if (unlikely(capacity< 0)) {
if (likely(capacity == -ENOMEM)) {
if (net_ratelimit())
dev_warn(&dev->dev,
- "TX queue failure: out of memory\n");
+ "TXQ (%d) failure: out of memory\n",
+ qnum);
} else {
dev->stats.tx_fifo_errors++;
if (net_ratelimit())
dev_warn(&dev->dev,
- "Unexpected TX queue failure: %d\n",
- capacity);
+ "Unexpected TXQ (%d) failure: %d\n",
+ qnum, capacity);
}
dev->stats.tx_dropped++;
kfree_skb(skb);
return NETDEV_TX_OK;
}
- virtqueue_kick(vi->svq);
+ virtqueue_kick(vq);

/* Don't wait up for transmitted skbs to be freed. */
skb_orphan(skb);
@@ -661,13 +721,13 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
/* Apparently nice girls don't return TX_BUSY; stop the queue
* before it gets out of hand. Naturally, this wastes entries. */
if (capacity< 2+MAX_SKB_FRAGS) {
- netif_stop_queue(dev);
- if (unlikely(!virtqueue_enable_cb_delayed(vi->svq))) {
+ netif_stop_subqueue(dev, qnum);
+ if (unlikely(!virtqueue_enable_cb_delayed(vq))) {
/* More just got used, free them then recheck. */
- capacity += free_old_xmit_skbs(vi);
+ capacity += free_old_xmit_skbs(vi, vq);
if (capacity>= 2+MAX_SKB_FRAGS) {
- netif_start_queue(dev);
- virtqueue_disable_cb(vi->svq);
+ netif_start_subqueue(dev, qnum);
+ virtqueue_disable_cb(vq);
}
}
}
@@ -700,7 +760,8 @@ static struct rtnl_link_stats64 *virtnet_stats(struct net_device *dev,
unsigned int start;

for_each_possible_cpu(cpu) {
- struct virtnet_stats *stats = per_cpu_ptr(vi->stats, cpu);
+ struct virtnet_stats __percpu *stats
+ = per_cpu_ptr(vi->stats, cpu);
u64 tpackets, tbytes, rpackets, rbytes;

do {
@@ -734,20 +795,26 @@ static struct rtnl_link_stats64 *virtnet_stats(struct net_device *dev,
static void virtnet_netpoll(struct net_device *dev)
{
struct virtnet_info *vi = netdev_priv(dev);
+ int i;

- napi_schedule(&vi->napi);
+ for (i = 0; i< vi->num_queue_pairs; i++)
+ napi_schedule(&vi->rq[i]->napi);
}
#endif

static int virtnet_open(struct net_device *dev)
{
struct virtnet_info *vi = netdev_priv(dev);
+ int i;

- /* Make sure we have some buffers: if oom use wq. */
- if (!try_fill_recv(vi, GFP_KERNEL))
- queue_delayed_work(system_nrt_wq,&vi->refill, 0);
+ for (i = 0; i< vi->num_queue_pairs; i++) {
+ /* Make sure we have some buffers: if oom use wq. */
+ if (!try_fill_recv(vi->rq[i], GFP_KERNEL))
+ queue_delayed_work(system_nrt_wq,
+ &vi->rq[i]->refill, 0);
+ virtnet_napi_enable(vi->rq[i]);
+ }

- virtnet_napi_enable(vi);
return 0;
}

@@ -809,10 +876,13 @@ static void virtnet_ack_link_announce(struct virtnet_info *vi)
static int virtnet_close(struct net_device *dev)
{
struct virtnet_info *vi = netdev_priv(dev);
+ int i;

/* Make sure refill_work doesn't re-enable napi! */
- cancel_delayed_work_sync(&vi->refill);
- napi_disable(&vi->napi);
+ for (i = 0; i< vi->num_queue_pairs; i++) {
+ cancel_delayed_work_sync(&vi->rq[i]->refill);
+ napi_disable(&vi->rq[i]->napi);
+ }

return 0;
}
@@ -924,11 +994,10 @@ static void virtnet_get_ringparam(struct net_device *dev,
{
struct virtnet_info *vi = netdev_priv(dev);

- ring->rx_max_pending = virtqueue_get_vring_size(vi->rvq);
- ring->tx_max_pending = virtqueue_get_vring_size(vi->svq);
+ ring->rx_max_pending = virtqueue_get_vring_size(vi->rq[0]->vq);
+ ring->tx_max_pending = virtqueue_get_vring_size(vi->sq[0]->vq);
ring->rx_pending = ring->rx_max_pending;
ring->tx_pending = ring->tx_max_pending;
-
}


@@ -961,6 +1030,19 @@ static int virtnet_change_mtu(struct net_device *dev, int new_mtu)
return 0;
}

+/* To avoid contending a lock hold by a vcpu who would exit to host, select the
+ * txq based on the processor id.
+ */
+static u16 virtnet_select_queue(struct net_device *dev, struct sk_buff *skb)
+{
+ int txq = skb_rx_queue_recorded(skb) ? skb_get_rx_queue(skb) :
+ smp_processor_id();
+
+ while (unlikely(txq>= dev->real_num_tx_queues))
+ txq -= dev->real_num_tx_queues;
+ return txq;
+}
+
static const struct net_device_ops virtnet_netdev = {
.ndo_open = virtnet_open,
.ndo_stop = virtnet_close,
@@ -972,6 +1054,7 @@ static const struct net_device_ops virtnet_netdev = {
.ndo_get_stats64 = virtnet_stats,
.ndo_vlan_rx_add_vid = virtnet_vlan_rx_add_vid,
.ndo_vlan_rx_kill_vid = virtnet_vlan_rx_kill_vid,
+ .ndo_select_queue = virtnet_select_queue,
#ifdef CONFIG_NET_POLL_CONTROLLER
.ndo_poll_controller = virtnet_netpoll,
#endif
@@ -1007,10 +1090,10 @@ static void virtnet_config_changed_work(struct work_struct *work)

if (vi->status& VIRTIO_NET_S_LINK_UP) {
netif_carrier_on(vi->dev);
- netif_wake_queue(vi->dev);
+ netif_tx_wake_all_queues(vi->dev);
} else {
netif_carrier_off(vi->dev);
- netif_stop_queue(vi->dev);
+ netif_tx_stop_all_queues(vi->dev);
}
done:
mutex_unlock(&vi->config_lock);
@@ -1023,41 +1106,217 @@ static void virtnet_config_changed(struct virtio_device *vdev)
queue_work(system_nrt_wq,&vi->config_work);
}

-static int init_vqs(struct virtnet_info *vi)
+static void free_receive_bufs(struct virtnet_info *vi)
+{
+ int i;
+
+ for (i = 0; i< vi->num_queue_pairs; i++) {
+ while (vi->rq[i]->pages)
+ __free_pages(get_a_page(vi->rq[i], GFP_KERNEL), 0);
+ }
+}
+
+/* Free memory allocated for send and receive queues */
+static void virtnet_free_queues(struct virtnet_info *vi)
{
- struct virtqueue *vqs[3];
- vq_callback_t *callbacks[] = { skb_recv_done, skb_xmit_done, NULL};
- const char *names[] = { "input", "output", "control" };
- int nvqs, err;
+ int i;

- /* We expect two virtqueues, receive then send,
- * and optionally control. */
- nvqs = virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ) ? 3 : 2;
+ for (i = 0; i< vi->num_queue_pairs; i++) {
+ kfree(vi->rq[i]);
+ vi->rq[i] = NULL;
+ kfree(vi->sq[i]);
+ vi->sq[i] = NULL;
+ }
+}

- err = vi->vdev->config->find_vqs(vi->vdev, nvqs, vqs, callbacks, names);
- if (err)
- return err;
+static void free_unused_bufs(struct virtnet_info *vi)
+{
+ void *buf;
+ int i;
+
+ for (i = 0; i< vi->num_queue_pairs; i++) {
+ struct virtqueue *vq = vi->sq[i]->vq;
+
+ while ((buf = virtqueue_detach_unused_buf(vq)) != NULL)
+ dev_kfree_skb(buf);
+ }
+
+ for (i = 0; i< vi->num_queue_pairs; i++) {
+ struct virtqueue *vq = vi->rq[i]->vq;
+
+ while ((buf = virtqueue_detach_unused_buf(vq)) != NULL) {
+ if (vi->mergeable_rx_bufs || vi->big_packets)
+ give_pages(vi->rq[i], buf);
+ else
+ dev_kfree_skb(buf);
+ --vi->rq[i]->num;
+ }
+ BUG_ON(vi->rq[i]->num != 0);
+ }
+}
+
+static void virtnet_set_affinity(struct virtnet_info *vi, bool set)
+{
+ int i;
+
+ if (vi->num_queue_pairs == 1)
+ return;
+
+ for (i = 0; i< vi->num_queue_pairs; i++) {
+ int cpu = set ? i : -1;
+ virtqueue_set_affinity(vi->rq[i]->vq, cpu);
+ virtqueue_set_affinity(vi->sq[i]->vq, cpu);
+ }
+ return;
+}
+
+static void virtnet_del_vqs(struct virtnet_info *vi)
+{
+ struct virtio_device *vdev = vi->vdev;
+
+ virtnet_set_affinity(vi, false);
+
+ vdev->config->del_vqs(vdev);
+
+ virtnet_free_queues(vi);
+}
+
+static int virtnet_find_vqs(struct virtnet_info *vi)
+{
+ vq_callback_t **callbacks;
+ struct virtqueue **vqs;
+ int ret = -ENOMEM;
+ int i, total_vqs;
+ char **names;

- vi->rvq = vqs[0];
- vi->svq = vqs[1];
+ /*
+ * We expect 1 RX virtqueue followed by 1 TX virtqueue, followd by
+ * possible control virtqueue and followed by the same
+ * 'vi->num_queue_pairs-1' more times
+ */
+ total_vqs = vi->num_queue_pairs * 2 +
+ virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ);
+
+ /* Allocate space for find_vqs parameters */
+ vqs = kmalloc(total_vqs * sizeof(*vqs), GFP_KERNEL);
+ callbacks = kmalloc(total_vqs * sizeof(*callbacks), GFP_KERNEL);
+ names = kmalloc(total_vqs * sizeof(*names), GFP_KERNEL);
so this needs to be kzalloc otherwise on an error cleanup will
get uninitialized data and crash?

Yes, will change it to use kzalloc.

+ if (!vqs || !callbacks || !names)
+ goto err;
+
+ /* Parameters for control virtqueue, if any */
+ if (vi->has_cvq) {
+ callbacks[2] = NULL;
+ names[2] = "control";
+ }
+
+ /* Allocate/initialize parameters for send/receive virtqueues */
+ for (i = 0; i< vi->num_queue_pairs * 2; i += 2) {
+ int j = (i == 0 ? i : i + vi->has_cvq);
+ callbacks[j] = skb_recv_done;
+ callbacks[j + 1] = skb_xmit_done;
+ names[j] = kasprintf(GFP_KERNEL, "input.%d", i / 2);
+ names[j + 1] = kasprintf(GFP_KERNEL, "output.%d", i / 2);
This needs wrappers. E.g. virtnet_rx_vq(int queue_pair), virtnet_tx_vq(int queue_pair);
Then you would just scan 0 to num_queue_pairs, and i is queue pair
number.

Ok.
+ }

- if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ)) {
+ ret = vi->vdev->config->find_vqs(vi->vdev, total_vqs, vqs, callbacks,
+ (const char **)names);
+ if (ret)
+ goto err;
+
+ if (vi->has_cvq)
vi->cvq = vqs[2];

- if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VLAN))
- vi->dev->features |= NETIF_F_HW_VLAN_FILTER;
+ for (i = 0; i< vi->num_queue_pairs * 2; i += 2) {
+ int j = i == 0 ? i : i + vi->has_cvq;
+ vi->rq[i / 2]->vq = vqs[j];
+ vi->sq[i / 2]->vq = vqs[j + 1];
Same here.

Consider the code is really simple, seem no need to use helpers.

}
- return 0;
+
+err:
+ if (ret&& names)
If we are here ret != 0. For names, just add another label, don't
complicate cleanup.

Ok.
+ for (i = 0; i< vi->num_queue_pairs * 2; i++)
+ kfree(names[i]);
+
+ kfree(names);
+ kfree(callbacks);
+ kfree(vqs);
+
+ return ret;
+}
+
+static int virtnet_alloc_queues(struct virtnet_info *vi)
+{
+ int ret = -ENOMEM;
+ int i;
+
+ for (i = 0; i< vi->num_queue_pairs; i++) {
+ vi->rq[i] = kzalloc(sizeof(*vi->rq[i]), GFP_KERNEL);
+ vi->sq[i] = kzalloc(sizeof(*vi->sq[i]), GFP_KERNEL);
+ if (!vi->rq[i] || !vi->sq[i])
+ goto err;
+ }
+
+ ret = 0;
+
+ /* setup initial receive and send queue parameters */
+ for (i = 0; i< vi->num_queue_pairs; i++) {
+ vi->rq[i]->vi = vi;
+ vi->rq[i]->pages = NULL;
+ INIT_DELAYED_WORK(&vi->rq[i]->refill, refill_work);
+ netif_napi_add(vi->dev,&vi->rq[i]->napi, virtnet_poll,
+ napi_weight);
+
+ sg_init_table(vi->rq[i]->sg, ARRAY_SIZE(vi->rq[i]->sg));
+ sg_init_table(vi->sq[i]->sg, ARRAY_SIZE(vi->sq[i]->sg));
+ }
+
Add return 0 here, then ret = 0 will not be needed
above and if (ret) below.


Ok.
+err:
+ if (ret)
+ virtnet_free_queues(vi);
+
+ return ret;
+}
+
+static int virtnet_setup_vqs(struct virtnet_info *vi)
+{
+ int ret;
+
+ /* Allocate send& receive queues */
+ ret = virtnet_alloc_queues(vi);
+ if (!ret) {
+ ret = virtnet_find_vqs(vi);
+ if (ret)
+ virtnet_free_queues(vi);
+ else
+ virtnet_set_affinity(vi, true);
+ }
+
+ return ret;
Add some labels for error handling, this if nesting is messy.

Ok.
}

static int virtnet_probe(struct virtio_device *vdev)
{
- int err;
+ int i, err;
struct net_device *dev;
struct virtnet_info *vi;
+ u16 num_queues, num_queue_pairs;
+
+ /* Find if host supports multiqueue virtio_net device */
+ err = virtio_config_val(vdev, VIRTIO_NET_F_MULTIQUEUE,
+ offsetof(struct virtio_net_config,
+ num_queues),&num_queues);
+
+ /* We need atleast 2 queue's */
typo

Will fix this, thanks.
+ if (err || num_queues< 2)
+ num_queues = 2;
+ if (num_queues> MAX_QUEUES * 2)
+ num_queues = MAX_QUEUES;
+
+ num_queue_pairs = num_queues / 2;

/* Allocate ourselves a network device with room for our info */
- dev = alloc_etherdev(sizeof(struct virtnet_info));
+ dev = alloc_etherdev_mq(sizeof(struct virtnet_info), num_queue_pairs);
if (!dev)
return -ENOMEM;

@@ -1103,22 +1362,18 @@ static int virtnet_probe(struct virtio_device *vdev)

/* Set up our device-specific information */
vi = netdev_priv(dev);
- netif_napi_add(dev,&vi->napi, virtnet_poll, napi_weight);
vi->dev = dev;
vi->vdev = vdev;
vdev->priv = vi;
- vi->pages = NULL;
vi->stats = alloc_percpu(struct virtnet_stats);
err = -ENOMEM;
if (vi->stats == NULL)
- goto free;
+ goto free_netdev;

- INIT_DELAYED_WORK(&vi->refill, refill_work);
mutex_init(&vi->config_lock);
vi->config_enable = true;
INIT_WORK(&vi->config_work, virtnet_config_changed_work);
- sg_init_table(vi->rx_sg, ARRAY_SIZE(vi->rx_sg));
- sg_init_table(vi->tx_sg, ARRAY_SIZE(vi->tx_sg));
+ vi->num_queue_pairs = num_queue_pairs;

/* If we can receive ANY GSO packets, we must allocate large ones. */
if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO4) ||
@@ -1129,9 +1384,17 @@ static int virtnet_probe(struct virtio_device *vdev)
if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
vi->mergeable_rx_bufs = true;

- err = init_vqs(vi);
+ if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ))
+ vi->has_cvq = true;
+
How about we disable multiqueue if there's no cvq?
Will make logic a bit simpler, won't it?

We can, but as you said, just let the logic simpler a bit.
+ /* Allocate/initialize the rx/tx queues, and invoke find_vqs */
+ err = virtnet_setup_vqs(vi);
if (err)
- goto free_stats;
+ goto free_netdev;
+
+ if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ)&&
+ virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VLAN))
+ dev->features |= NETIF_F_HW_VLAN_FILTER;

err = register_netdev(dev);
if (err) {
@@ -1140,12 +1403,15 @@ static int virtnet_probe(struct virtio_device *vdev)
}

/* Last of all, set up some receive buffers. */
- try_fill_recv(vi, GFP_KERNEL);
-
- /* If we didn't even get one input buffer, we're useless. */
- if (vi->num == 0) {
- err = -ENOMEM;
- goto unregister;
+ for (i = 0; i< num_queue_pairs; i++) {
+ try_fill_recv(vi->rq[i], GFP_KERNEL);
+
+ /* If we didn't even get one input buffer, we're useless. */
+ if (vi->rq[i]->num == 0) {
+ free_unused_bufs(vi);
+ err = -ENOMEM;
+ goto free_recv_bufs;
+ }
}

/* Assume link up if device can't report link status,
@@ -1158,42 +1424,25 @@ static int virtnet_probe(struct virtio_device *vdev)
netif_carrier_on(dev);
}

- pr_debug("virtnet: registered device %s\n", dev->name);
+ pr_debug("virtnet: registered device %s with %d RX and TX vq's\n",
+ dev->name, num_queue_pairs);
+
return 0;

-unregister:
+free_recv_bufs:
+ free_receive_bufs(vi);
unregister_netdev(dev);
+
free_vqs:
- vdev->config->del_vqs(vdev);
-free_stats:
- free_percpu(vi->stats);
-free:
+ for (i = 0; i< num_queue_pairs; i++)
+ cancel_delayed_work_sync(&vi->rq[i]->refill);
+ virtnet_del_vqs(vi);
+
+free_netdev:
free_netdev(dev);
return err;
}

-static void free_unused_bufs(struct virtnet_info *vi)
-{
- void *buf;
- while (1) {
- buf = virtqueue_detach_unused_buf(vi->svq);
- if (!buf)
- break;
- dev_kfree_skb(buf);
- }
- while (1) {
- buf = virtqueue_detach_unused_buf(vi->rvq);
- if (!buf)
- break;
- if (vi->mergeable_rx_bufs || vi->big_packets)
- give_pages(vi, buf);
- else
- dev_kfree_skb(buf);
- --vi->num;
- }
- BUG_ON(vi->num != 0);
-}
-
static void remove_vq_common(struct virtnet_info *vi)
{
vi->vdev->config->reset(vi->vdev);
@@ -1201,10 +1450,9 @@ static void remove_vq_common(struct virtnet_info *vi)
/* Free unused buffers in both send and recv, if any. */
free_unused_bufs(vi);

- vi->vdev->config->del_vqs(vi->vdev);
+ free_receive_bufs(vi);

- while (vi->pages)
- __free_pages(get_a_page(vi, GFP_KERNEL), 0);
+ virtnet_del_vqs(vi);
}

static void __devexit virtnet_remove(struct virtio_device *vdev)
@@ -1230,6 +1478,7 @@ static void __devexit virtnet_remove(struct virtio_device *vdev)
static int virtnet_freeze(struct virtio_device *vdev)
{
struct virtnet_info *vi = vdev->priv;
+ int i;

/* Prevent config work handler from accessing the device */
mutex_lock(&vi->config_lock);
@@ -1237,10 +1486,13 @@ static int virtnet_freeze(struct virtio_device *vdev)
mutex_unlock(&vi->config_lock);

netif_device_detach(vi->dev);
- cancel_delayed_work_sync(&vi->refill);
+ for (i = 0; i< vi->num_queue_pairs; i++)
+ cancel_delayed_work_sync(&vi->rq[i]->refill);

if (netif_running(vi->dev))
- napi_disable(&vi->napi);
+ for (i = 0; i< vi->num_queue_pairs; i++)
+ napi_disable(&vi->rq[i]->napi);
+

remove_vq_common(vi);

@@ -1252,19 +1504,22 @@ static int virtnet_freeze(struct virtio_device *vdev)
static int virtnet_restore(struct virtio_device *vdev)
{
struct virtnet_info *vi = vdev->priv;
- int err;
+ int err, i;

- err = init_vqs(vi);
+ err = virtnet_setup_vqs(vi);
if (err)
return err;

if (netif_running(vi->dev))
- virtnet_napi_enable(vi);
+ for (i = 0; i< vi->num_queue_pairs; i++)
+ virtnet_napi_enable(vi->rq[i]);

netif_device_attach(vi->dev);

- if (!try_fill_recv(vi, GFP_KERNEL))
- queue_delayed_work(system_nrt_wq,&vi->refill, 0);
+ for (i = 0; i< vi->num_queue_pairs; i++)
+ if (!try_fill_recv(vi->rq[i], GFP_KERNEL))
+ queue_delayed_work(system_nrt_wq,
+ &vi->rq[i]->refill, 0);

mutex_lock(&vi->config_lock);
vi->config_enable = true;
@@ -1287,7 +1542,7 @@ static unsigned int features[] = {
VIRTIO_NET_F_GUEST_ECN, VIRTIO_NET_F_GUEST_UFO,
VIRTIO_NET_F_MRG_RXBUF, VIRTIO_NET_F_STATUS, VIRTIO_NET_F_CTRL_VQ,
VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN,
- VIRTIO_NET_F_GUEST_ANNOUNCE,
+ VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MULTIQUEUE,
};

static struct virtio_driver virtio_net_driver = {
diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index 1bc7e30..60f09ff 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -61,6 +61,8 @@ struct virtio_net_config {
__u8 mac[6];
/* See VIRTIO_NET_F_STATUS and VIRTIO_NET_S_* above */
__u16 status;
+ /* Total number of RX/TX queues */
+ __u16 num_queues;
} __attribute__((packed));

/* This is the first element of the scatter-gather list. If you don't
--
1.7.1

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